Researches have been made on the characteristics of an organic matter since the late 1970's and technologies for making organic matters to have conductivity through doping were introduced. Accordingly, many organic matters having conductivity were introduced and such organic matters were used to develop various devices, such as organic solar batteries, organic emitting light displays, organic thin film transistors, and capacitor elements. Also, the development of polyacetylene, conjugated organic polymer, makes it possible to easily form organic semiconductors in fibers or in a film, and the organic semiconductors have many advantages, such as flexibility, conductivity, and a low manufacturing cost. Due to such characteristics of the organic semiconductor, the organic semiconductors have been adapted to various application fields, for example, a functional electronic devices and optical devices. Particularly, an organic thin film transistor (OTFT) has been used as a core part in various application fields, such as, a rollable display, a smart card, and a radio frequency (RF) tag.
The performance of an organic thin film depends on the crystallinity of an organic active thin film. The crystallinity depends on a growing process of a thin film and the surface condition of a gate insulating layer where an organic thin film is grown. According to the analysis of the organic devices, the adhesive force and the interfacial property, such as crystallinity and interfacial illuminance, between a substrate and an electrode and between an electrode and an organic insulating layer, and electric characteristics, such as interfacial properties, have been recognized as major factors to be improved.
The gate electrode of an organic thin film transistor according to the related art was made of metal. Such a metal electrode had high reflectivity and was weak physically. Therefore, it is necessary to develop a new device as a gate electrode instead of the metal electrode.